Sulfur removal from oils

The sulfur removed during coal combustion generates gypsum (see below) and slag material. Slag has no commercial value. By contrast, the sulfur removed from oil and gas can often be recovered in the form of useful materials, including elemental sulfur. NO , is not usually removed, but a small proportion may be retained during FGD. 

A process innovation was introduced by Valentine [61], who added an SOx sorbent for mitigating the inhibiting effects of the formed oxysulfides. This process was developed for sulfur removal from extra heavy oils, bitumens, and its emulsions, such as the trade mark Orimulsion. Any active biocatalyst may be used in this process carried out at temperatures close to 50°C. The main features disclosed in patents protecting the use of R. rhodochrous-bas d biocatalysts, in desulfurization reactions are summarized in Table 12. 

Desulfurization of two LGO streams was studied using R. erythropolis rKA2-5-l [71] to determine the rate of desulfurization and develop a predictive model for desulfurization of diesel oil. The sulfur removal from various substituted DBTs was modeled using a competitive inhibition and lumping model and the desulfurization of the LGO streams was successfully assessed. The model consisted of a four component system based on... 

Atlantic Richfield Company, Arco has developed several conventional technologies for sulfur removal from coal and ashes and for manufacturing oil-coal mixed fuels, prior to becoming involved in BDS. Their patent entitled, Biodesulfurization of carbonaceous materials [16] was developed for the coal application, but nevertheless was extrapolated for application to petroleum desulfurization as well. 

Much of the sulfur contained in a crude oil remains with the tar, asphalt or coke after refining. As crude prices rise, even this residuum becomes valuable as a feedstock for cracking to make lighter products. This involves deep desulfurization. Whether the coke is burned as a fuel or used for anodes, desulfurization will take place before or after combustion or processing. Sulfur removal from coke plants is a currently feasible process. 

It is also doubtful that the industry will be in a position for many years to come to undertake sulfur removal from residual fuels solely to improve product quality. A number of consumer industries demand low sulfur fuel oils, but these special requirements can at present be met more appropriately by selection of crude rather than by adoption of desulfurization processes. In general industrial use, it is corrosion and atmospheric pollution that are the main disadvantages of high sulfur content. But there is no sign yet of the development of a cheap desulfurization process, the cost of which can be substantially offset by the gain in efficiency resulting from permissible lower stack temperatures or by the elimination of flue gas scrubbing equipment previously necessary for reduction of sulfur dioxide content. 

Oil - [COALCONVERSIONPROCESSES - CARBONIZATION] (Vol6) - [COALCONVERSIONPROCESSES - GASIFICATION] (Vol6) - [SIZE ENLARGEMENT] (Vol 22) -fuel for limestone kilns [LIME AND LIMESTONE] (Vol 15) -hydrogen from [HYDROGEN] (Vol 13) -measurement of particles m [SIZE MEASUREMENT OF PARTICLES] (V ol 22) -m nuts [NUTS] (Vol 17) -as petroleum lubricant [LUBRICATION AND LUBRICANTS] (Vol 15) -pipeline transport [PIPELINES] (Vol 19) -sample analysis by ms [MASS SPECTROMETRY] (Vol 15) -from shale [OIL SHALE] (Vol 17) -steel quenching m [STEEL] (Vol 22) -sulfur removal from [SULFUR] (Vol 23) -tanks for [TANKS AND PRESSURE VESSELS] (Vol 23) -use of fluidization [FLUIDIZATION] (Vol 11)... 

Some of the first studies on the biodegradation of sulfur compounds focused on their fate and removal from oil-contaminated environments. Another major area of study is the microbial process of "biodesulfurization" which has been suggested as a means of selectively removing sulfur compounds from petroleum prior to refining. Information gathered from these two areas of research provide the basis of the present knowledge of metabolism of organosulfur compounds in petroleum. This information is reviewed with emphasis on the metabolism of dibenzothiophenes and n-alkyl tetrahydrothiophenes (n-alkyl thiolanes). 

Data on the nature and yield of the hydrocarbon product are not available, although the process has been stated to have operated successfully on a semiplant scale with paraffin-base oils. That it has not yet been superlatively successful may be deduced from the lack of its widespread use. The possibility of sulfur removal from high sulfur crudes, such as the West Texas crudes, by such a process has probably been investigated but no authoritative information is available. It is probable that such an oxidation process will not greatly reduce the sulfur content in the product unless it is allowed to occur to an excessive extent. 

Table 3 provides a list of the extent of desulfurization of diesel range oils obtained with a number of desulfurization strains. Interestingly, there is a trend toward a higher percentage of sulfur removal from hydrotreated oils versus nonhydrotreated oils. The ability to remove a higher percentage of sulfur from an... 

The use of sorbents for sulfur removal dates back to the use of bauxite (i.e., the ore for aluminum smelting) to adsorb mercaptans from various petroleum fractions (Purdy, 1958). Red mud (the iron-rich waste from the Bayer process for alumina extraction from bauxite) has also been used as a sorbent for sulfur removal from petroleum oils. 

Sulfur Removal from Crude Oil and its Fraction, Fig. 3 Typical gas phase composition... 

This refinery depended on twin plants to recover sulfur removed from the crude oil. The Environmental Protection Agency regulates emissions in refineries, and the ability to recover sulfur can and has limited refinery throughput. 

Lubricating Oil Extraction. Aromatics are removed from lubricating oils to improve viscosity and chemical stabihty (see Lubrication and lubricants). The solvents used are furfural, phenol, and Hquid sulfur dioxide. The latter two solvents are undesirable owing to concerns over toxicity and the environment and most newer plants are adopting furfural processes (see Furan derivatives). A useful comparison of the various processes is available (219). 

Cmde gas leaves from the top of the gasifier at 288—593°C depending on the type of coal used. The composition of gas also depends on the type of coal and is notable for the relatively high methane content when contrasted to gases produced at lower pressures or higher temperatures. These gas products can be used as produced for electric power production or can be treated to remove carbon dioxide and hydrocarbons to provide synthesis gas for ammonia, methanol, and synthetic oil production. The gas is made suitable for methanation, to produce synthetic natural gas, by a partial shift and carbon dioxide and sulfur removal. 

The largest use of NMP is in extraction of aromatics from lube oils. In this appHcation, it has been replacing phenol and, to some extent, furfural. Other petrochemical uses involve separation and recovery of aromatics from mixed feedstocks recovery and purification of acetylenes, olefins, and diolefins removal of sulfur compounds from natural and refinery gases and dehydration of natural gas. 

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